ABSTRACT
Analysis of surface water treatment practice in the Netherlands shows that cyanobacteria, especially Microcystis aeruginosa and Oscillatoria agardhii, are the main problem causing algae. Conventional (sedimentation) and advanced (dissolved air flotation) treatment of algae laden (model) water were studied. The agglomeration (coagulation/flocculation) phase was found to determine the process efficiency and hence to be the prerequisite for process improvement. Both processes were assessed in terms of their removal efficiency for the cyanobacterium M. aeruginosa. Relevant process parameters were studied, including the influence of coagulant (FeCl3) dose, coagulation pH, flocculation time, energy input (G value), single-stage versus tapered flocculation, application of a cationic polyelectrolyte (Superfloc C-573) as coagulant aid, and surface loading. The process efficiency was assessed as a function of the agglomeration and the resultant particle (floc) size distributions. The results were evaluated in function of highlighting the occurring process mechanisms.
